The present invention relates generally to forming closed tubular structures, and more particularly to using folded sheet stock having flanges welded prior to placement within a die to provide a predetermined shape.
In a typical metal forming operation in which closed sections are formed, conventional methods utilize either a combination of a stamping and a welding process of sheet metal to form the closed tubular section or a hydroforming process. In the stamping/welding process, two portions of the closed section are stamped individually from the sheet metal. The two portions are then aligned and welded to form the closed tubular section. Such, a process, however, leaves a tubular section having two welds, which provides a greater opportunity for heat deformation requires metal and reduction techniques.
In a hydroforming process, the tubular member is folded, welded, and placed in a die. Fluid pressure is then applied within the interior of the tubular member, causing the tubular member to expand to fill the die. In the hydroform process, however, expansion is typically limited to 25 to 30%. This limitation of expansion causes a corresponding limitation in the variability of the cross-section over the length of the tubular member. Thus, it is desirable to provide an improved process for forming tubular members.
It is also desirable to provide a process at which results in the formation of a tubular member having a cross-section along its length that can be varied, which is welded on only one seam, and which has minimal sharp surfaces.
This invention is directed to a process for forming a tubular metal section in a predetermined shape. The process includes providing sheet metal and folding the sheet metal to form a generally open tube with a pair of opposing flanges. the opposing flanges are welded at various, predetermined locations along the flanges. The welded sheet meal is placed into a die formed to the predetermined shape, and the sheet metal is expanded within the die outwardly toward the die to form the tubular metal section in the predetermined shape.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.